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#170845 - 11/13/07 02:21 PM Did anyone from NZ notice this?
Trumpy Offline

Member

Registered: 07/05/02
Posts: 8540
Loc: SI,New Zealand
I happened to be reading one of the recent "Electron" newsletters from the EWRB mailed out to us registered folks when this little pearl of wisdom stood out at me.
Apparently, to harmonise our cable ratings with those of Aussie, NZS 6401 will be revoked, this standard gives our building wiring cables (round and flat) their 600/1000V voltage rating, that is the maximum voltage between cores is 600V and between cores and earth is 1000V.
Now, under the new AS/NZS 5000:2:2006 cables will have a maximum voltage rating of 450/750V.
Now, I have some concern about this idea and I find it strange that there was never any consultation with those of us here that would actually be using the cables in question.
I've noticed over the last couple of years, the insulation on TPS cables is getting thinner, especially with composite (XLPE) cables.
It also makes me wonder if there hasn't been some sort of lobbying effort on the part of cable manufacturers in this issue, especially when you consider that cheaper imports are driving down the cost of cables sold in our DIY stores.
I'm only thinking about this from a safety aspect, if a new standard is introduced that allows a lower voltage rating and hence thinner insulation are we going to see more installations with damaged cables due to poor installation practice?
I agree that the 600/1000V rating is slightly over the top, but it has meant that we've had that bit more of a comfort zone in the past.
What's your opinion on this issue?.

Edit:Here's a link to the document (PDF) with the story in it:
October Electron


Edited by Trumpy (11/13/07 02:23 PM)
Edit Reason: To add link
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#170857 - 11/13/07 05:38 PM Re: Did anyone from NZ notice this? [Re: Trumpy]
aussie240 Offline
Member

Registered: 07/06/05
Posts: 222
Loc: Blue Mountains, NSW, Australia
Interesting newsletter...I think we can safely say the reduction in cable quality is the result of the usual cost comes before quality scenario with most manufactured goods. The insulation on modern TPS worries me; I can't believe it's as durable as back in the days when 4mm was really 4mm and not what looks like 2.5mm. And don't get me started on 1.5mm...that might well as be light duty speaker flex these days, and just as fragile.
What's with the 110V RV's & caravans mentioned? I've never heard of this in Australia. Are they Japanese grey imports? Are they actually fitted with 110V appliances and US style fittings? (100V to be correct if they are Jap). Surely that would be an inconvenience to the owner not being able to use their normal appliances, to say nothing of getting spare 110V light bulbs.

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#170861 - 11/13/07 05:58 PM Re: Did anyone from NZ notice this? [Re: aussie240]
Trumpy Offline

Member

Registered: 07/05/02
Posts: 8540
Loc: SI,New Zealand
Aussie,
That refers to tourists bringing in their own appliances and transformers and using them in either a caravan or camper-van that are designed to run on 230VAC.
This sounds like an accident just waiting to happen and I'm surprised it hasn't already when you consider the market for travel adaptors.
Certification of caravan wiring is something that really worries me and I try and avoid it if possible.
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#170898 - 11/14/07 09:57 AM Re: Did anyone from NZ notice this? [Re: Trumpy]
pauluk Offline
Member

Registered: 08/11/01
Posts: 7693
Loc: Norfolk, England
 Originally Posted By: Trumpy
their 600/1000V voltage rating, that is the maximum voltage between cores is 600V and between cores and earth is 1000V.


Shouldn't that be the other way round?

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#170903 - 11/14/07 02:30 PM Re: Did anyone from NZ notice this? [Re: pauluk]
Trumpy Offline

Member

Registered: 07/05/02
Posts: 8540
Loc: SI,New Zealand
 Originally Posted By: pauluk
 Originally Posted By: Trumpy
their 600/1000V voltage rating, that is the maximum voltage between cores is 600V and between cores and earth is 1000V.


Shouldn't that be the other way round?

Actually, that's a very good question, Paul.
AFAIK, it is correct as I've typed it, I could be wrong too.
What's more, I can find no information to back this assertion up, I've just looked through the Olex and General Cable literature that I have here and can find no reference to this actual rating.
I'm only going by what I was taught at night school in the earlier part of my training.
I'll see what I can find on the Net.
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#170920 - 11/14/07 09:38 PM Re: Did anyone from NZ notice this? [Re: Trumpy]
RODALCO Offline
Member

Registered: 12/08/05
Posts: 863
Loc: Titirangi, Akld, New Zealand
Good topic Mike.

I noticed that a while ago too, about 2 years ago, when buying a drum of 2.5 mm² TPS at Bunnings, that the rating was lower 450/750 Volts.
It had the approved labels on the drum and checked with an inspector I know that this cable is already on the market.

The Electron notice i did read too. It is typical from bureaucracies to lower standards, perhaps allowing now substandard Chinese cable to enter our NZ market, and penalising electricians harsly on COC's while the cowboys can do what they want and get away scot free.

Also the cable is not rated for a standard 500 Vdc Megger insulation test.
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#170921 - 11/14/07 10:37 PM Re: Did anyone from NZ notice this? [Re: RODALCO]
Trumpy Offline

Member

Registered: 07/05/02
Posts: 8540
Loc: SI,New Zealand
 Originally Posted By: RODALCO
Also the cable is not rated for a standard 500 Vdc Megger insulation test.

Huh?, I never thought of that aspect of the voltage rating.

Now lets be real here, 230VAC is the RMS voltage of the supply we receive, the peak voltage is somewhat higher, that would be getting rather close to the maximum voltage rating of the cable, between cores.

This whole issue in my opinion is something being fixed that isn't even broken in the first place.
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#170929 - 11/15/07 05:09 AM Re: Did anyone from NZ notice this? [Re: Trumpy]
Texas_Ranger Offline
Member

Registered: 12/17/01
Posts: 2343
Loc: Vienna, Austria
Lemme think... IIRC most stuff in Europ is only 300/500V! Zip cord is even 300/300V! And yes, that's below the peak of 230V RMS.

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#170961 - 11/15/07 05:23 PM Re: Did anyone from NZ notice this? [Re: Texas_Ranger]
pauluk Offline
Member

Registered: 08/11/01
Posts: 7693
Loc: Norfolk, England
The ratings are for A.C. RMS, so no problem.

But they are 300V to ground / 500V between conductors, or British S.W.A. is 600/1000V -- 600V to ground, 1000V between conductors.

That's why the "reverse" N.Z. rating seems wrong to me.

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#171119 - 11/20/07 12:22 AM Re: Did anyone from NZ notice this? [Re: pauluk]
Trumpy Offline

Member

Registered: 07/05/02
Posts: 8540
Loc: SI,New Zealand
Well then Paul,
It seems I have been wrong all along. \:\(
These two FAQ's from the Olex Australian site, sum things up:

 Quote:
What does the .6/1kV designation mean?

This is the method adopted generally by Australia, UK, Asia and Europe in indicating the voltage rating of a cable. The first number indicates the voltage rating of the insulation to ground and the second number indicates the voltage rating from one insulated conductor to another insulated conductor. Generally if a cable is only referred to by one voltage, the second number is used. For example a 19/33kV cable is often referred to as a 33kV cable.

Why are generally used cables designated as 450/750V when only 240 volts are being carried?

A minimum thickness of insulation is required to offer a reasonable level of resistance to mechanical damage. If only enough insulation was used to insulate to 240 volts, the covering would be too easily damaged.
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